Method for active control of frequency and voltage in a power supply grid with decentralized power supply systems

Abstract

The invention relates to a method for actively controlling in a feedback control at least one output parameter (f i , V i , P i , Q i ) of a decentralized power generating unit ( 1 ) feeding power into a power supply grid ( 14 ) having a plurality of such decentralized power generating units, the power generating unit ( 1 ) being coupled to the grid ( 14 ) at a grid tied point ( 16 ). The actual resistance (R i ), reactance (X i ) and magnitude (|Z i |) of the impedance (Z i ) of the power generating unit ( 1 ) at the tied point ( 16 ) is determined and a first quotient (R i /|Z i |) between the resistance (R i ) and impedance magnitude (|Z i |) and a second quotient (X i /|Z i |) between the reactance (X i ) and the impedance magnitude (|Z i |) is calculated. These quotients (R i /|Z i |, X i /|Z i |) are used for the feedback control of the at least one output parameter (f i , V i , P i , Q i ).

1 . A method for actively controlling in a feedback control at least one output parameter of a decentralized power generating unit feeding power into a power supply grid having a plurality of such decentralized power generating units, the power generating unit being coupled to the grid at a grid tied point, wherein the actual resistance, reactance and magnitude of the impedance of the power generating unit at the tied point is determined and a first quotient between the resistance and impedance magnitude and a second quotient between the reactance and the impedance magnitude is calculated and used for the feedback control of the at least one output parameter. 
     
     
         2 . The method according to  claim 1 , wherein the controlled output parameter is the frequency of the power generating unit and that the method comprises the steps of:
 determining the actual active power and reactive power of the power generating unit that are fed into the grid at the grid tied point,   calculating the active power difference between the actual active power delivered from the power generating unit and a given reference active power,   calculating the reactive power difference between the actual active power delivered from the power generating unit and a given reference active power,   using the second quotient to calculate a first frequency product of the active power difference, the second quotient and a given frequency droop factor,   using the first quotient to calculate a second frequency product of the reactive power difference, the first quotient and the frequency droop factor, and   calculating the sum of the first and the negative second frequency product to get a frequency correction term which is added to the error of the feedback control of the frequency.   
     
     
         3 . The method according to  claim 1 , wherein the controlled output parameter is the voltage of the power generating unit and that the method comprises the steps of:
 determining the actual active power and reactive power of the power generating unit that are fed into the grid at the grid tied point,   calculating the active power difference between the actual active power delivered from the power generating unit and a given reference active power,   calculating the reactive power difference between the actual active power delivered from the power generating unit and a given reference active power,   using the first quotient to calculate a first voltage product of the active power difference, the first quotient and a given voltage droop factor,   using the second quotient to calculate a second voltage product of the reactive power difference, the second quotient and the voltage droop factor, and   calculating the sum of the first and the second voltage product to get a voltage correction term which is added to the error of the feedback control of the voltage.   
     
     
         4 . The method according to  claim 1 , wherein the controlled output parameter is the active power of the power generating unit and that the method comprises the steps of:
 determining the actual frequency and voltage of the power generating unit at the grid tied point,   calculating the frequency difference between the actual frequency of the power generating unit and a given reference frequency,   calculating the voltage difference between the actual voltage of the power generating unit and a given reference voltage,   using the second quotient to calculate a first active power product of the frequency difference, the second quotient and a given active power droop factor,   using the first quotient to calculate a second active power product of the voltage difference, the first quotient and the active power droop factor, and   calculating the sum of the first and the negative second active power product to get an active power correction term which is added to the error of the feedback control of the active power.   
     
     
         5 . The method according to  claim 1 , wherein the controlled output parameter is the reactive power of the power generating unit and that the method comprises the steps of:
 determining the actual frequency and voltage of the power generating unit at the grid tied point,   calculating the frequency difference between the actual frequency of the power generating unit and a given reference frequency,   calculating the voltage difference between the actual voltage of the power generating unit and a given reference voltage,   using the first quotient to calculate a first reactive power product of the frequency difference, the first quotient and a given reactive power droop factor,   using the second quotient to calculate a second reactive power product of the voltage difference, the second quotient and the reactive power droop factor, and   calculating the sum of the first and the second reactive power product to get a reactive power correction term which is added to the error of the feedback control of the reactive power.   
     
     
         6 . The method according to  claim 4 , wherein the active power droop factor equals the inverted value of the frequency droop factor. 
     
     
         7 . The method according to  claim 5 , wherein the reactive power droop factor (???,?) equals the inverted value of the voltage droop factor. 
     
     
         8 . The method according to  claim 1 , wherein
 the frequency and the voltage or the active power and the reactive power of each decentralized power generating unit of the grid is controlled using the first quotient and the second quotient is used for the feedback control of the parameters.   
     
     
         9 . The method according to  claim 2 , wherein the active power difference is filtered by a selective function before it is used for calculating a product. 
     
     
         10 . The method according to  claim 2  wherein the reactive power difference is filtered by a selective function before it is used for calculating a product. 
     
     
         11 . The method according to  claim 4  wherein the frequency difference is filtered by a selective function before it is used for calculating a product. 
     
     
         12 . The method according to  claim 4 , wherein the voltage difference is filtered by a selective function before it is used for calculating a product. 
     
     
         13 . Use of the method according to  claim 1 , wherein the method is implemented in a power generating unit for extra high voltage, high voltage, medium voltage or low voltage. 
     
     
         14 . Use of the method according to  claim 1 , wherein the method is carried out in a power system with inductive or resistive nature. 
     
     
         15 . The use of the method according  claim 1 , wherein the method is carried out in the control of a synchronous motor or an inverter. 
     
     
         16 . The use of the method according to  claim 1 , wherein the method is carried out in the control of a one phase or three phase inverter.